Positive active material, method of preparing the same, and lithium secondary battery including the same

A positive active material comprising:

• lithium;
• a transition metal;
• oxygen;
• lithium (Li) layers;
• transition metal layers;
• and
• a doping metal including boron,
• wherein:
• the lithium layers include a first lithium layer including only lithium and a second lithium layer in which at least a part of the lithium of the first lithium layer is alternately substituted with the transition metal,
• the transition metal layer includes a first transition metal layer including only the transition metal, and a second transition metal layer in which at least a part of the first transition metal layer is alternately substituted with lithium,
• the second lithium layers and the second transition metal layers are alternately and repeatedly provided,
• in the second lithium layer, a half of the lithium of the first lithium layer is substituted with the transition metal,
• in the second transition metal layer, a half of the transition metal of the first transition metal layer is substituted with lithium,
• the transition metal of the second lithium layer is obtained through an exchange of the transition metal of the first transition metal layer and the lithium of the second lithium layer, so that the lithium and the transition metal of the second lithium layer are alternately and repeatedly arranged, and the transition metal and the lithium of the second transition metal layer are alternately and repeatedly provided while corresponding to the lithium and the transition metal of the second lithium layer, respectively,
• a lattice formed by the second lithium layer and the second transition metal layer is a superlattice with an a-axis length two times an a-axis length of the lattice formed by the first lithium layer and the first transition metal layer, the superlattice consisting of a plurality of repeating units each including six lithium elements and only one transition metal element,
• the transition metal includes nickel, and one or more of cobalt, and manganese, thereby allowing surplus peaks to be generated within the superlattice;
• the nickel is 79 mol % or more;
• an a-axis of a lattice formed by the second lithium layer and the second transition metal layer includes a lattice with long-range ordering corresponding to the plurality of repeating units, and
• substitution energy of the lithium and the transition metal decreases by the doping metal.

A positive active material comprising:

• lithium;
• a transition metal;
• oxygen;
• lithium (Li) layers;
• and
• transition metal layers,
• wherein:
• the lithium layers include a first lithium layer including only lithium and a second lithium layer in which at least a part of the lithium of the first lithium layer is alternately substituted with the transition metal,
• the transition metal layer includes a first transition metal layer including only the transition metal, and a second transition metal layer in which at least a part of the first transition metal layer is alternately substituted with lithium,
• the second lithium layers and the second transition metal layers are alternately and repeatedly provided,
• in the second lithium layer, a half of the lithium of the first lithium layer is substituted with the transition metal,
• in the second transition metal layer, a half of the transition metal of the first transition metal layer is substituted with lithium,
• the transition metal of the second lithium layer is obtained through an exchange of the transition metal of the first transition metal layer and the lithium of the second lithium layer, so that the lithium and the transition metal of the second lithium layer are alternately and repeatedly arranged, and the transition metal and the lithium of the second transition metal layer are alternately and repeatedly provided while corresponding to the lithium and the transition metal of the second lithium layer, respectively,
• a lattice formed by the second lithium layer and the second transition metal layer is a superlattice with an a-axis length two times an a-axis length of the lattice formed by the first lithium layer and the first transition metal layer,
• the transition metal includes nickel, and one or more of cobalt, and manganese, thereby allowing surplus peaks to be generated within the superlattice;
• the nickel is 79 mol % or more;
• the superlattice consists of a plurality of repeating units each including six lithium elements and only one transition metal element, and
• an a-axis of a lattice formed by the second lithium layer and the second transition metal layer includes a lattice with long-range ordering corresponding to the plurality of repeating units.